CADDIS FLIES AND SPRING-TAILS. 573 



The caddis worms, as they are called, live in ponds and ditches, and make 

 themselves cases of stick, or small stones and shells, bound together, and 

 lined with silk, and in these they, live, and undergo their metamorphoses. 



Wingless Insects, allied to Neuroptera. 



There are three groups of wingless insects, which are sometimes classed 

 with the Neuroptera, and are sometimes treated separately. They are as 

 follows : 



The Mallophaga are placed by some authors with the Anoplura, or true lice, 

 as an aberrant family of Hemiptera, but others place them with the Neur- 

 optera, and others again treat them as a distinct order. 

 They much resemble the lice, but differ from them in pos- Bird Lice (Mal- 

 sessing well-developed mandibles. They have large flat- iophaga). 

 tened bodies, large heads, and rather short legs. They 

 infest different species of birds, feeding on the soft part of the feathers near 

 the quills. Most of them are of rather small size ; the largest, which are 

 nearly half an inch in length, infest the eagles, vultures, and albatrosses. 



The Thysanura and Collembola are two small orders or sub-orders of 

 wingless insects, which have long, jointed antennae, and six legs, but under- 

 go no metamorphoses. The Thysanura have an apparatus 



Spring Tails for leaping at the end of the body, and are frequently called 

 ( Thysanura). spring tails. The best known, however, is 



the silver fish, Lepisma saceharina (Linn.), a Silver Fish, 

 silvery-grey insect, about half an inch long, often found in 

 crevices in dark corners in houses, where it darts about with great activity 

 when disturbed. 



ORDER HYMENOPTERA (BEES, WASPS, ANTS, ETC.). 



In this Order we find insects with four wings, which are generally long and 

 narrow, and frequently clothed with short hairs, only visible under the 

 microscope. The fore and hind wings are often linked to- 

 gether by a row of small links, which has suggested the Structure and 

 name of the order. The veins of the wings are never very Metamorphoses, 

 numerous, nor is the neuration complicated. In many 

 families, however, the females and sometimes both sexes are wingless, and 

 in others there is a race of imperfectly developed females, called neuters 

 or workers, which are frequently wingless. The ovipositor of the female is 

 modified either into a sting, or into a boring apparatus, which, in the latter 

 case, is sometimes of great length. There are usually three ocelli, or simple 

 eyes on the vertex in addition to the two large lateral compound eyes. The 

 metamorphoses are complete, and the pupa is inactive, and necromorphous, 

 as in Coleoptera, the limbs being encased in separate immovable sheaths. 

 The pupa is usually enclosed in a cocoon. 



The Hymenoptera include a large number of insects, which, though very 

 diversified in form and habits, have still such a strong family likeness that 

 they cannot easily be mistaken for insects of any other order. Some are 

 vegetable-feeders, like the saw-flies, the larvae of which so much resemble 

 caterpillars that they have been not inaptly termed " false caterpillars " ; the 

 larvae of the wood-wasps burrow in the wood of trees ; the gall-flies form 



